Metal to metal seal for downhole tools

ABSTRACT

A metal to metal seal for downhole tools. A sealing device includes a metal seal. A nonmetal seal may be used to bias the metal seal in a radial direction in response to a pressure differential applied to the sealing device. A well tool includes a housing assembly, a closure member and the sealing device. Both of the metal and nonmetal seals contact a selected one of the housing assembly and closure member when the closure member blocks flow through the housing assembly. A method of sealing between the housing assembly and closure member includes the step of displacing the closure member to relieve the pressure differential, the metal seal continuing to seal against the pressure differential until the nonmetal seal no longer seals between the housing assembly and the closure member.

TECHNICAL FIELD

The present invention relates generally to equipment utilized andoperations performed in conjunction with a subterranean well and, in anembodiment described herein, more particularly provides a metal seal fordownhole tools.

BACKGROUND

Metal seals are sometimes used to seal between structures in well tools,and in equipment used in other environments. However, several problemsare frequently encountered when metal seals are used. For example, metalseals require very smooth and clean surfaces to seal against, and mostmetals can only be elastically deformed to a limited extent (whichthereby limits the biasing force available from elastically deforming ametal seal), etc.

Elastomeric and other types of nonmetal seals may provide the ability toseal against irregular and unclean surfaces, and may provide sufficientresilient biasing force for urging the seals against the surfaces.However, nonmetal seals tend to degrade rapidly when used in dynamicconfigurations, i.e., where the seal must contact a moving surface whilesealing against a pressure differential, or where the seal loses contactwith the surface while the pressure differential still exists across theseal.

Therefore, it may be seen that improvements are needed in the art ofsealing devices.

SUMMARY

In carrying out the principles of the present invention, a sealingdevice is provided which solves at least one problem in the art. Oneexample is described below in which the sealing device includes both ametal seal and an elastomer seal. Another example is described below inwhich elastomer seals are used to energize metal seals in response topressure differentials in different directions.

In one aspect of the invention, a sealing device is provided. Thesealing device includes at least one metal seal. A nonmetal seal may beused to bias the metal seal in a radial direction in response to apressure differential applied to the sealing device.

In another aspect of the invention, a well tool is provided whichincludes a housing assembly and a closure member. A sealing device isused for sealing between the housing assembly and closure member. Thesealing device includes at least one metal seal and at least onenonmetal seal. Both of the metal and nonmetal seals contact one of thehousing assembly and closure member when the closure member blocks flowthrough the housing assembly.

A method of sealing between a housing assembly and a closure member isalso provided by the invention. The method includes the steps of:providing a sealing device including at least one metal seal and atleast one nonmetal seal; applying a pressure differential across thesealing device while the sealing device seals between the housingassembly and the closure member; and displacing the closure member torelieve the pressure differential. The metal seal continues to sealagainst the pressure differential until the nonmetal seal no longerseals between the housing assembly and the closure member.

These and other features, advantages, benefits and objects of thepresent invention will become apparent to one of ordinary skill in theart upon careful consideration of the detailed description ofrepresentative embodiments of the invention hereinbelow and theaccompanying drawings, in which similar elements are indicated in thevarious figures using the same reference numbers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic partially cross-sectional view of a well systemembodying principles of the present invention;

FIG. 2 is an enlarged scale cross-sectional view of a closure mechanismof a flow control device in the well system;

FIG. 3 is a further enlarged scale cross-sectional view of a sealingdevice for use in the closure mechanism;

FIG. 4 is an enlarged scale cross-sectional view of an alternateconfiguration of the closure mechanism; and

FIG. 5 is a further enlarged scale cross-sectional view of an alternateconfiguration of the sealing device for use in the closure mechanism ofFIG. 4.

DETAILED DESCRIPTION

It is to be understood that the various embodiments of the presentinvention described herein may be utilized in various orientations, suchas inclined, inverted, horizontal, vertical, etc., and in variousconfigurations, without departing from the principles of the presentinvention. The embodiments are described merely as examples of usefulapplications of the principles of the invention, which is not limited toany specific details of these embodiments.

In the following description of the representative embodiments of theinvention, directional terms, such as “above”, “below”, “upper”,“lower”, etc., are used for convenience in referring to the accompanyingdrawings. In general, “above”, “upper”, “upward” and similar terms referto a direction toward the earth's surface along a wellbore, and “below”,“lower”, “downward” and similar terms refer to a direction away from theearth's surface along the wellbore.

Representatively illustrated in FIG. 1 is a well system 10 whichembodies principles of the present invention. In the well system 10, atubular string 12 (such as a production tubing string) is positioned ina wellbore 14 lined with casing 16. The tubular string 12 includes welltools 18, 20.

The well tool 18 is a packer, and the well tool 20 is a flow controldevice (such as a valve or choke). The packer provides an annular sealbetween the tubular string 12 and the casing 16, and the flow controldevice regulates fluid communication between the interior of the tubularstring and an annulus 22 formed between the tubular string and thecasing. The flow control device includes a closure mechanism 24 which isoperated to regulate flow.

At this point, it should be reiterated that the invention is not limitedto any of the details of the well system 10 described herein. Forexample, it is not necessary for the invention to be used in a wellbore,in a well tool, in a cased wellbore, in a flow control device, in atubular string, etc. The closure mechanism 24 could, as another example,be used in a hydraulic setting device of the packer 18, or could be usedin another type of well tool. Thus, it should be clearly understood thatthe well system 10 is only a single example of a wide variety of usesfor the principles of the invention.

Referring additionally now to FIG. 2, an enlarged scale cross-sectionalview of a portion of the well tool 20 is representatively illustrated.In this view it may be seen that the closure mechanism 24 includes atubular closure member 26 which is displaced relative to a housingassembly 28 to thereby regulate flow through openings 30 in the housingassembly.

To completely block flow through the openings 30, the closure member 26engages a sealing device 34. The sealing device 34 operates to provide aseal between the closure member 26 and the housing assembly 28 tothereby prevent flow through the openings 30.

In one important feature of the sealing device 34, both metal seals 32a, 32 b and nonmetal seals 36 a, 36 b are included in the device. Theseseals 32 a, 32 b, 36 a, 36 b contact and seal against the closure member26 when the closure member is in the position depicted in FIG. 2.However, it will be appreciated that the sealing device 34 could becarried on, and displace with, the closure member 26, so that the seals32 a, 32 b, 36 a, 36 b could contact and seal against the housingassembly 28 when the closure member is in the position depicted in FIG.2, if desired.

Note that a separate seal 38 is shown sealing between the sealing device34 and the housing assembly 28. However, it will be appreciated thatthis seal 38 could be incorporated into the sealing device 34, ifdesired. For example, the nonmetal seals 36 a, 36 b could extend furtherradially outward into sealing contact with the housing assembly 28,and/or a seal could be formed by metal to metal contact between thehousing assembly and an outer ring 40 of the device 34.

Referring additionally now to FIG. 3, a further enlarged cross-sectionalview of the sealing device 34 is representatively illustrated. In thisview it may be more clearly seen that the metal seals 32 a, 32 b eachinclude an inclined beam or arm 42 a, 42 b extending between a sealsurface 44 a, 44 b and the ring 40. It may also be seen that each of thenonmetal seals 36 a, 36 b includes a generally wedge-shaped portion 46a, 46 b positioned between the ring 40 and a respective one of the arms42 a, 42 b.

The metal seals 32 a, 32 b are preferably made of strong, durable andresilient metals, such as Inconel 718, 13-chrome steel, etc. Thenonmetal seals 36 a, 36 b are preferably made of high temperature andwell fluid resistant, strong and elastomeric materials, such as NBR,HNBR, fluoroelastomers, etc. Non-elastomeric materials, such as PEEK,etc., may additionally or alternatively be used in the nonmetal seals 36a, 36 b. It should be clearly understood that any metal materials may beused for the metal seals 32 a, 32 b, and any nonmetal materials may beused for the nonmetal seals 36 a, 36 b, in keeping with the principlesof the invention.

Note that the nonmetal seals 36 a, 36 b are not necessary for thesealing device 34 to seal between the housing assembly 28 and theclosure member 26. The sealing device 34 could be provided without thenonmetal seals 36 a, 36 b, in which case the metal seals 32 a, 32 bwould still provide sealing engagement with the closure member 26. Useof the nonmetal seals 36 a, 36 b is preferred when a bubble-tightsealing engagement is required.

When the closure member 26 engages the sealing device 34 as depicted inFIG. 2, the seal surfaces 44 a, 44 b contact the outer surface of theclosure member and the arms 42 a, 42 b are deflected radially outwardsomewhat. This deflection causes elastic deformation of the arms 42 a,42 b, resulting in a biasing force being applied by the arms to the sealsurfaces 44 a, 44 b. Note that the seal surfaces 44 a, 44 b have smallridges formed thereon to concentrate this radial biasing force on arelatively small area, thereby increasing the contact pressure betweenthe seal surfaces and the outer surface of the closure member 26. Itshould be understood, however, that use of the small ridges is notrequired on the seal surfaces 44 a, 44 b.

The nonmetal seals 36 a, 36 b are also radially compressed between thering 40 and the outer surface of the closure member 26. In this manner,a seal surface 48 a, 48 b on each nonmetal seal 36 a, 36 b is biasedinto sealing contact with the outer surface of the closure member 26.

Deflection of the arms 42 a, 42 b as described above will compress thewedge portion 46 a, 46 b of each nonmetal seal between the ring 40 andthe respective arm. If the nonmetal seals 36 a, 36 b are made of aresilient material, this compression will result in a radial biasingforce being applied to each arm, thereby further biasing the sealsurfaces 44 a, 44 b into contact with the outer surface of the closuremember 26.

When a pressure differential 50 is applied across the sealing device 34in an upward direction as depicted in FIG. 3, the wedge portion 46 b ofthe lower nonmetal seal 36 b will be further compressed between the ring40 and the arm 42 b of the lower metal seal 32 b. This compression ofthe lower wedge portion 46 b will result in a further radial biasingforce being applied to the arm, thereby further biasing the lower sealsurface 44 b into contact with the outer surface of the closure member26.

When a pressure differential 52 is applied across the sealing device 34in an downward direction as depicted in FIG. 3, the wedge portion 46 aof the upper nonmetal seal 36 a will be further compressed between thering 40 and the arm 42 a of the upper metal seal 32 a. This compressionof the upper wedge portion 46 a will result in a further radial biasingforce being applied to the arm, thereby further biasing the upper sealsurface 44 a into contact with the outer surface of the closure member26.

Thus, it will be appreciated that each of the sealing surfaces 44 a, 44b is radially biased into metal to metal sealing contact with the outersurface of the closure member 26 due to: 1) elastic deformation of therespective arm 42 a, 42 b, 2) compression of the respective wedgeportion 46 a, 46 b between the ring 40 and the respective arm due todeformation of the arm, and 3) compression of the respective wedgeportion 46 a, 46 b due to the pressure differential 50 or 52. Thisresults in reliable metal to metal sealing between the metal seals 32 a,32 b and the outer surface of the closure member 26.

If, however, the seal surfaces 44 a, 44 b or the outer surface of theclosure member 26 should become damaged, so that metal to metal sealingtherebetween cannot be achieved, sealing contact between the nonmetalseals 36 a, 36 b and the closure member may still be possible.

In another important feature of the sealing device 34, note that, as theclosure member 26 displaces upward from its closed position depicted inFIG. 2, sealing contact with the closure member is progressively removedfrom the lower nonmetal seal 36 b, then the lower metal seal 32 b, thenthe upper metal seal 32 a, and then the upper nonmetal seal 36 a. Thismeans that, if the differential pressure 50 or 52 is applied against thesealing device 34 when the closure member 26 displaces upward, thepressure differential across the lower nonmetal seal 36 b will berelieved while the other seals 32 a, 32 b, 36 a maintain sealing contactwith the closure member. This prevents damage to the seal 36 b fromexcessive flow when the pressure differential 50 or 52 is relieved.

When the closure member 26 eventually displaces upward sufficiently farthat it no longer is in sealing contact with the upper nonmetal seal 36a, and the pressure differential across this seal is thus relieved, theclosure member will still be contained within a closely fitted sleeve 66in which the openings 30 are formed, thereby preventing damage to theseal from excessive flow.

As the closure member 26 displaces downward from its open position inwhich flow is permitted through the openings 30, the pressuredifferential 50 or 52 may be applied when the closure member sealinglyengages the sealing device 34. The pressure differential 50 or 52 willfirst be applied to the upper nonmetal seal 36 a while the closuremember 26 remains within the closely fitted sleeve 66, therebypreventing damage to the seal from excessive flow. Next, in succession,the closure member 26 sealingly contacts the upper metal seal 32 a, thelower metal seal 32 b, and the lower nonmetal seal 36 b.

It may now be fully appreciated that the sealing device 34 providessignificant benefits in performing the sealing function in the closuremechanism 24 of the well tool 20. For example, the metal seals 32 a, 32b provide for metal to metal sealing between the closure member 26 andthe housing assembly 28, the metal seals are resiliently biased intosealing contact in multiple ways (including an increased biasing forceas the differential pressure across the sealing device 34 increases),and the nonmetal seals 36 a, 36 b provide for additional sealingcapability in the event that metal to metal sealing cannot be achieved.Pressure differentials from either direction across the sealing device34 can be sealed against, without damage to the seals 32 a, 32 b, 36 a,36 b, whether the closure member 26 displaces to close or open while thepressure differential exists.

Referring additionally now to FIG. 4, an alternate configuration of theclosure mechanism 24 is representatively illustrated. This alternateconfiguration of the closure mechanism 24 includes an alternateconfiguration of the sealing device 34, which is depicted in a furtherenlarged cross-sectional view in FIG. 5.

The sealing device 34 as illustrated in FIG. 5 is similar in somerespects to the sealing device of FIG. 3, in that it includes multiplemetal seals 54 a, 54 b with respective seal surfaces 56 a, 56 b andinclined beams or arms 58 a, 58 b extending between the seal surfacesand a ring 60.

The sealing device 34 of FIG. 5 also includes multiple nonmetal seals 62a, 62 b positioned between the metal seals 54 a, 54 b. A wedge portion64 a, 64 b of each respective nonmetal seal 62 a, 62 b is positionedbetween a respective one of the arms 58 a, 58 b and the ring 60.

A difference between the nonmetal seals 62 a, 62 b and the nonmetalseals 36 a, 36 b described above is that the seals 62 a, 62 b are formedas a single, integral element, rather than as separate elements. Indeedthe nonmetal seals 62 a, 62 b could be formed as a single seal, ifdesired. Furthermore, as discussed above for the nonmetal seals 36 a, 36b, use of the nonmetal seals 62 a, 62 b is not required in the sealingdevice 34 of FIGS. 4 & 5.

As with the configuration of FIGS. 2 & 3, the seal surfaces 56 a, 56 bof the metal seals 54 a, 54 b are radially biased into sealing contactwith the outer surface of the closure member 26 due to elasticdeformation of the arms 58 a, 58 b and resulting compression of thewedge portions 64 a, 64 b of the nonmetal seals 62 a, 62 b between thearms and the ring 60. However, further biasing forces applied to thearms 58 a, 58 b due to differential pressure across the sealing device34 occurs somewhat differently in the alternate configuration of FIGS. 4& 5.

When the closure member 26 is in its closed position as depicted in FIG.4, the pressure differential 50 will cause the wedge portion 64 a of thenonmetal seal 62 a to further compress between the arm 58 a and the ring60, thereby applying a biasing force to the arm and further biasing theseal surface 56 a against the outer surface of the closure member. Whenthe pressure differential 52 is applied across the sealing device 34,the wedge portion 64 b of the nonmetal seal 62 b will be furthercompressed between the arm 58 b and the ring 60, thereby applying abiasing force to the arm and further biasing the seal surface 56 bagainst the outer surface of the closure member.

As the closure member 26 displaces upward from its closed positiondepicted in FIG. 4, sealing contact with the closure member isprogressively removed from the lower metal seal 54 b, then the lowernonmetal seal 62 b, then the upper nonmetal seal 62 a, and then theupper metal seal 54 a. This means that, if the differential pressure 50or 52 is applied against the sealing device 34 when the closure member26 displaces upward, the pressure differential across the nonmetal seals62 a, 62 b will be relieved (after the pressure differential is relievedacross the lower metal seal 54 b) while the upper metal seal 54 amaintains sealing contact with the closure member. This prevents damageto the seals 62 a, 62 b from excessive flow when the pressuredifferential 50 or 52 is relieved.

When the closure member 26 eventually displaces upward sufficiently farthat it no longer is in sealing contact with the upper metal seal 54 a,and the pressure differential across this seal is thus relieved, theclosure member will still be contained within the closely fitted sleeve66, thereby preventing damage to the seal from excessive flow.

As the closure member 26 displaces downward from its open position inwhich flow is permitted through the openings 30, the pressuredifferential 50 or 52 may be applied when the closure member sealinglyengages the sealing device 34. The pressure differential 50 or 52 willfirst be applied to the upper metal seal 54 a while the closure member26 remains within the closely fitted sleeve 66, thereby preventingdamage to the seal from excessive flow. Next, in succession, the closuremember 26 sealingly contacts the upper nonmetal seal 62 a, the lowernonmetal seal 62 b, and the lower metal seal 54 b.

It will be appreciated that the sealing device 34 in the configurationof FIGS. 4 & 5 provides similar benefits to those of the configurationof FIGS. 2 & 3. For example, the metal seals 54 a, 54 b provide formetal to metal sealing between the closure member 26 and the housingassembly 28, the metal seals are resiliently biased into sealing contactin multiple ways (including an increased biasing force as thedifferential pressure across the sealing device 34 increases), and thenonmetal seals 62 a, 62 b provide for additional sealing capability inthe event that metal to metal sealing cannot be achieved. Pressuredifferentials from either direction across the sealing device 34 can besealed against, without damage to the seals 54 a, 54 b, 62 a, 62 b,whether the closure member 26 displaces to closed or open positionswhile the pressure differential exists.

Sealing devices constructed in accordance with the principles of theinvention should be capable of sealing against 15,000 psi differentialpressure at 325-400° F. in a static condition (no movement of theclosure member relative to the housing assembly), and should be capableof reliably sealing against 1500-5000 psi during opening and closing ofthe closure member.

Of course, a person skilled in the art would, upon a carefulconsideration of the above description of representative embodiments ofthe invention, readily appreciate that many modifications, additions,substitutions, deletions, and other changes may be made to the specificembodiments, and such changes are contemplated by the principles of thepresent invention. Accordingly, the foregoing detailed description is tobe clearly understood as being given by way of illustration and exampleonly, the spirit and scope of the present invention being limited solelyby the appended claims and their equivalents.

1. A well tool, comprising: a housing assembly; a closure member; and asealing device for sealing between the housing assembly and closuremember, the sealing device including at least one metal seal, the metalseal contacting a selected one of the housing assembly and closuremember when the closure member blocks flow through the housing assembly.2. The well tool of claim 1, wherein the sealing device further includesat least one nonmetal seal, and wherein the nonmetal seal biases themetal seal against the selected one of the housing assembly and closuremember in response to a first pressure differential across the sealingdevice.
 3. The well tool of claim 2, wherein the nonmetal seal biasesthe metal seal against the selected one of the housing assembly andclosure member in response to a second pressure differential across thesealing device, the first and second pressure differentials beingoppositely directed relative to each other.
 4. The well tool of claim 1,wherein the metal seal includes an arm which elastically deforms,thereby biasing the metal seal against the selected one of the housingassembly and the closure member, when the closure member blocks flowthrough the housing assembly.
 5. The well tool of claim 1, wherein thesealing device includes first and second metal seals, and at least afirst nonmetal seal.
 6. The well tool of claim 5, wherein the firstnonmetal seal is positioned between the first and second metal seals. 7.The well tool of claim 1, wherein the sealing device includes first andsecond metal seals, and first and second nonmetal seals.
 8. The welltool of claim 7, wherein the first and second metal seals are positionedbetween the first and second nonmetal seals.
 9. A sealing device,comprising: at least one metal seal; and at least one nonmetal seal, afirst nonmetal seal being operative to bias a first metal seal in aradial direction in response to a first pressure differential applied tothe sealing device in a first direction.
 10. The sealing device of claim9, wherein the first nonmetal seal is operative to bias a second metalseal in the radial direction in response to a second pressuredifferential applied to the sealing device in a second directionopposite to the first direction.
 11. The sealing device of claim 9,wherein a second nonmetal seal is operative to bias a second metal sealin the radial direction in response to a second pressure differentialapplied to the sealing device in a second direction opposite to thefirst direction.
 12. The sealing device of claim 9, wherein the firstnonmetal seal is positioned between first and second metal seals. 13.The sealing device of claim 9, wherein first and second metal seals arepositioned between the first nonmetal seal and a second nonmetal seal.14. The sealing device of claim 9, wherein the metal seal includes anarm which elastically deforms to bias the metal seal in the radialdirection.
 15. A method of sealing between a housing assembly and aclosure member, the method comprising the steps of: providing a sealingdevice including at least one metal seal and at least one nonmetal seal;applying a first pressure differential in a first direction across thesealing device while the sealing device seals between the housingassembly and the closure member; and displacing the closure member torelieve the first pressure differential, the metal seal continuing toseal against the first pressure differential until the nonmetal seal nolonger seals between the housing assembly and the closure member. 16.The method of claim 15, wherein the applying step further comprises afirst nonmetal seal biasing a first metal seal in a radial direction toseal against a selected one of the housing assembly and the closuremember.
 17. The method of claim 16, further comprising the step ofapplying a second pressure differential across the sealing device in asecond direction opposite to the first direction while the sealingdevice seals between the housing assembly and the closure member. 18.The method of claim 17, wherein the second pressure differentialapplying step further comprises the first nonmetal seal biasing a secondmetal seal in the radial direction to seal against the selected one ofthe housing assembly and the closure member.
 19. The method of claim 17,wherein the second pressure differential applying step further comprisesa second nonmetal seal biasing a second metal seal in the radialdirection to seal against the selected one of the housing assembly andthe closure member.
 20. The method of claim 15, wherein the displacingstep further comprises the first pressure differential being relievedacross a first nonmetal seal, then a first metal seal, then a secondmetal seal, and then a second nonmetal seal.
 21. The method of claim 15,wherein the displacing step further comprises the first pressuredifferential being relieved across a first metal seal, then a nonmetalseal, and then a second metal seal.
 22. The method of claim 15, furthercomprising the step of sealing between the closure device and thehousing assembly by elastically deforming an arm of the metal seal,thereby biasing the metal seal against a selected one of the closuredevice and housing assembly.
 23. The method of claim 22, wherein theapplying step further comprises the nonmetal seal applying a force tothe arm in response to the first pressure differential, thereby furtherbiasing the metal seal against the selected one of the closure deviceand housing assembly.
 24. A well tool, comprising: a housing assembly; aclosure member; and a sealing device for sealing between the housingassembly and closure member, the sealing device including at least onemetal seal and at least one nonmetal seal, both of the metal andnonmetal seals contacting a selected one of the housing assembly andclosure member when the closure member blocks flow through the housingassembly.
 25. The well tool of claim 24, wherein the nonmetal sealbiases the metal seal against the selected one of the housing assemblyand closure member in response to a first pressure differential acrossthe sealing device.
 26. The well tool of claim 25, wherein the nonmetalseal biases the metal seal against the selected one of the housingassembly and closure member in response to a second pressuredifferential across the sealing device, the first and second pressuredifferentials being oppositely directed relative to each other.
 27. Thewell tool of claim 24, wherein the metal seal includes an arm whichelastically deforms, thereby biasing the metal seal against the selectedone of the housing assembly and the closure member, when the closuremember blocks flow through the housing assembly.
 28. The well tool ofclaim 24, wherein the sealing device includes first and second metalseals, and at least a first nonmetal seal.
 29. The well tool of claim28, wherein the first nonmetal seal is positioned between the first andsecond metal seals.
 30. The well tool of claim 24, wherein the sealingdevice includes first and second metal seals, and first and secondnonmetal seals.
 31. The well tool of claim 30, wherein the first andsecond metal seals are positioned between the first and second nonmetalseals.